Remove WinPTY support

[laeubi]

WinPTY is no longer well supported and maybe even non functional anymore.

This is an attempt to remove it entirely, see comment here:

• missing Windows on Arm64 natives in CDT #969 (comment)

[jonahgraham]

I also cleaned up the Makefile to remove some references to now removed pty.dll.

This PR site on top of #1146 for the moment.

[jonahgraham]

Thanks @laeubi for doing this code cleanup. If/when we move this code to Platform having some of these items simplified will certainly help.

We also don't have the exact source used to build the winpty dll/exe that is in CDT. The source code may be in bugzilla, but the main place I know it to have been was in ipzilla. This has been fully archived and I don't even want to consider what it would take to get this source back out, let alone rebuild it. Therefore I am delighted to get this debt out of CDTs codebase.

Once #1146 is merged I will rebase and merge this too (assuming clean CI of course)

[github-actions]

Test Results

  585 files  ±0    585 suites  ±0   13m 43s ⏱️ -33s
9 914 tests ±0  9 890 ✅ ±0  24 💤 ±0  0 ❌ ±0 
9 952 runs  ±0  9 928 ✅ ±0  24 💤 ±0  0 ❌ ±0 

Results for commit 2f5548d. ± Comparison against base commit 8b22be8.